title: Optimisation of cardiac resynchronization therapy in clinical practice during exercise.
abstract: OBJECTIVE
  Although cardiac resynchronisation therapy (CRT) is an established treatment to improve cardiac function, a significant amount of patients do not experience noticeable improvement in their cardiac function. Optimal timing of the delay between atrial and ventricular pacing pulses (AV delay) is of major importance for effective CRT treatment and this optimum may differ between resting and exercise conditions. In this study the feasibility of haemodynamic measurements by the non-invasive finger plethysmographic method (Nexfin) was used to optimise the AV delay during exercise.
  
  
  RESULTS
  Thirty-one patients implanted with a CRT device in the last 4 years participated in the study. During rest and in exercise, stroke volume (SV) was measured using the Nexfin device for several AV delays. The optimal AV delay at rest and in exercise was determined using the least squares estimates (LSE) method. Optimisation created a clinically significant improvement in SV of 10 %. The relation between HR and the optimal AV delay was patient dependent.
  
  
  CONCLUSIONS
  A potential increase in SV of 10 % can be achieved using Nexfin for optimisation of AV delay during exercise. A considerable number of patients showed benefit with lengthening of the AV delay during exercise.
authors.affiliation: Thoraxcentrum Twente, Medisch Spectrum Twente, Haaksbergerstraat 55, 7513 ER, Enschede, the Netherlands, m.molenaar@mst.nl.
authors.forename: M M D
authors.initials: MM
authors.lastname: Molenaar
authors.forename: B
authors.initials: B
authors.lastname: Oude Velthuis
authors.forename: M F
authors.initials: MF
authors.lastname: Scholten
authors.forename: J Y
authors.initials: JY
authors.lastname: Stevenhagen
authors.forename: W A
authors.initials: WA
authors.lastname: Wesselink
authors.forename: J M
authors.initials: JM
authors.lastname: van Opstal